After headlining a fund-raiser Tuesday night with 600 guests at the home of Steve Louro on Smithtown Bay, the lovebirds were in Bridgehampton on Friday night at the Sandcastle, the estate that builder Joe Farrell has listed for $49.95 million.

“I’ve never been happier,” Guilfoyle told me. “I am thrilled to be joining Don Jr. across the country in amplifying the America-first message. We are working non-stop and we make the perfect team.”

One of the guests said the couple “arrived like royalty and worked the room together. They are a real power couple.”

Guilfoyle said it was an honor to travel across the country and see how America was becoming great again. She introduced Don Jr., and he told the crowd, “She’s a tough act to follow.”

Their co-hosts were Monica Crowley and House Majority Leader Kevin McCarthy.

On Monday night, the duo co-hosted a $50,000-per-couple fund-raiser with former Yankee pitcher Mariano Rivera at a Midtown restaurant for the America First Action PAC, of which Guilfoyle is vice chairwoman.